The 2004 SummerSlam was the 17th annual SummerSlam professional wrestling pay-per-view (PPV) event produced by World Wrestling Entertainment (WWE). It was held for wrestlers from the promotion's Raw and SmackDown! brand divisions. The event took place on August 15, 2004, at the Air Canada Centre in Toronto, Ontario, Canada. Nine matches were contested at the event, including one on the Sunday Night Heat pre-show. It was held during the 2004 Summer Olympics in Athens in reference to the promotional poster.

The main match on the Raw brand was Chris Benoit versus Randy Orton for the World Heavyweight Championship, which Orton won by pinfall after performing an RKO. The predominant match on the SmackDown! brand was John "Bradshaw" Layfield (JBL) versus The Undertaker for the WWE Championship, which JBL won after Undertaker was disqualified. The featured matches on the undercard included Kurt Angle versus Eddie Guerrero and Triple H versus Eugene.